Effective (n-6) Lennard-Jones Potentials with Temperature-Dependent Parameters Introduced for Accurate Calculation of Equilibrium and Transport Properties of Ethene, Propene, Butene, and Cyclopropane

Abstract

The alkenes and cycloalkanes C m H2m (m = 1 to 4) are important reactants, intermediates, and end products in the chemical industry. Some of them are also widely used in the polymer industry. This paper presents tables with recommended thermophysical data in the temperature range (200 to 1000) K and pressures ≤ 0.1 MPa of ethene, propene, cyclopropane, 1-butene, cis-2-butene, trans-2-butene, and iso-butene. Second pVT virial coefficients B, viscosities η, and diffusion coefficients D are calculated by means of a (n-6) Lennard-Jones temperature-dependent potential. The potential parameters, equilibrium distance R m(T), and potential well-depth ε(T) are defined as functions of the temperature T by solving an ill-posed problem of minimization of the squared deviations between measured and calculated B, η, and D, normalized to their experimental error. Tables with potential parameters as well as algorithms for calculation of the potential-dependent properties are given in this paper.

Characterization of Long Linear and Branched Alkanes and Alcohols for Temperatures up to 573.15 K by Surface Light Scattering and Molecular Dynamics Simulations

“…While the use of the generally assumed temperature-independent LJ parameters obtained in such a way provides reasonable predictions over limited temperature ranges considered in the fitting procedure, increasing deviations are likely to occur for temperatures outside the calibration ranges, as is also found in this work. By including a temperature dependence for the size and/or energy parameters of the LJ potential, the simulation results for the VLE and various thermophysical properties, including the vapor pressure, densities, virial coefficients, and viscosities for various types of gases and liquids, could be improved. − However, related studies have been applied for specific systems, assuming one effective interaction site for gases and relatively large molecules in the form of n -alkanes, cyclic and branched alkanes, and aromatic components with up to six carbon atoms. A transferability of the temperature-dependent LJ parameters to other familiar substances is, therefore, not or hardly possible.…”

A critical review of statistical calibration/prediction models handling data inconsistency and model inadequacy

“…Model inadequacy can sometimes be seen as a consequence of the use of a unique parameter set in different experimental conditions: a "better" model can indeed be obtained by using different values of the parameters along the control space. This can be achieved by modeling the dependence of the physical parameters on the control variable, [75][76][77] or by splitting the data in series along the control space and using a hierarchical model identical to the one in Section 3.2.2.2 for inference of the hyperparameters describing the model's parameters distribution (model M H2 in Wu et al 9 ). To differentiate both hierarchical schemes, the present one is named HierC.…”

Influence of the Sonication Temperature on the Debundling Kinetics of Carbon Nanotubes in Propan-2-ol

“…Van der Waals forces typically include interactions between atoms, molecules and close surfaces [ 22 ]. These interactions are typically derived from the Lennard Jones Potential (LJP) which is used to approximate the isotropic part of the van der Waals forces [ 47 , 48 ], corresponding in the list interaction types to both, attractive and repulsive terms, as a function of the distance between the objects. As CNTs are commonly considered to be non-polar [ 49 , 50 ] and slightly negatively charged [ 51 , 52 ] due to the curvature of their graphene walls, an approximate description of CNT/CNT interactions by means of London and Keesom’s forces combined is considered to be a simple and accurate approach [ 46 , 53 , 54 , 55 ].…”

“…As CNTs are commonly considered to be non-polar [ 49 , 50 ] and slightly negatively charged [ 51 , 52 ] due to the curvature of their graphene walls, an approximate description of CNT/CNT interactions by means of London and Keesom’s forces combined is considered to be a simple and accurate approach [ 46 , 53 , 54 , 55 ]. Recent work on the polymerization of low molecular weight alkenes showed the development of a temperature dependence parameter in the LJP [ 47 ] in order to explain the deviation of some thermo-physical and thermo-chemical properties when compared with predicted values. The modified model showed better agreement with experimental values.…”